controlling microbial growth

Terminology

• Sterilization: Removal of all microbial life

• Commercial Sterilization: Killing C. botulinum endospores

  • Aiming at killing C botulinum in our canned products

  • C botulinum makes botox, if it hits nerves wrongs gives paralysis, if it gets in guts food poising 

•  Disinfection: Removal of pathogens

  • Removing infectious agent 

• Antisepsis: Removal of pathogens from living tissue

  • Taking out infection in living tissue 

•  Degerming: Removal of microbes from a limited area

  • Removing things from a small area 

• Sanitization: Lower microbial counts on eating utensils

•  Biocide/Germicide: Kills microbes

  • Cidal = killing 

• Bacteriostasis: Inhibiting, not killing, microbes

  • stasis= only inhibiting not killing

What is the Removal of all microbial life

sterilization

What is Killing C. botulinum endospores

• Aiming at killing C botulinum in our canned products

• C botulinum makes botox, if it hits nerves wrongs gives paralysis, if it gets in guts food poising 

Commercial Sterilization

What is the removal of pathogens

• Removing infectious agent 

disinfection

What is  Removal of pathogens from living tissue

antisepsis

What is  Removal of microbes from a limited area

dergerming

What is  Lower microbial counts on eating utensils

sanitization

What kills microbes

 Biocide/Germicide

• cidal= killing

What is Inhibiting, not killing, microbes

Bacteriostasis

• stasis= only inhibitiing not killing

Bacterial populations die at what rate of growth

constant logarithmic rate

Effecitveness of antimicrobial treatments depends on:

• Number of micorbes

• Environment (organic matter, temp, concnetration, biofilms)

• Time of exposure

• Microbial characteristics (e.g. glycocalyx, cell wall, resistance)

Physical methods of microbial control:

• Heat: autoclaving

  • Moist heat denautres proteins

  • Autoclave: steam under pressure

  • 15 min at 121^o C at 15 psi

Moist heat does what

denatures proteins

What is steam under pressure?

autoclave

What temp is the autoclave set at and how long does it go for?

• 15 min at 121^o C at 15 psi

  • 15 psi (per square inch) raises up the temp by pressure

Pasteurization:

• 60^oC for 30 minutes
  72^oC for 15 seconds
  140^oC for 4 seconds
  Pasteurization reduces spoilage organisms and pathogens

  • ex: milk, beer

What does pasteurization do?

reduces spoilage organisms and pathogens

Physical methods of microbial control:

• Dry heat sterlizartion by oxidation

• Flaming

• Incineration

• Hot-air sterilzation

• Equal treatments

  • Hot-air 

    • 170^o C, 2 hr

  • Autoclave

    • 121^o C, 15 min

Physical methods of microbial control:

• filtration, low temp, high pressure, dessication, osmotic pressure

• Filtration removes microbes by trapping them in filter 

• Low temperature inhibits microbial growth

  • Refrigeration

  • Deep freezing (-20^o c or -80^o c)

  • Lypophilization

• High pressure denatures proteins

• Desiccation prevents metabolism

• osmotic pressure causes plasmolysis (shrinkage of cytoplasm)

Physical methods of microbial control:

Filtration does what

• removes microbes by trapping them in filter 

Physical methods of microbial control:

Low temperature does what

•  inhibits microbial growth

  • Refrigeration

  • Deep freezing (-20^o c or -80^o c)

  • Lypophilization

Physical methods of microbial control:

High pressure does what

• denatures proteins

Physical methods of microbial control:

Dessication does what

prevents metabolism

Physical methods of microbial control:

Osmotic pressure does what

causes plasmolysis (shrinkage of cytoplasm)

Physical methods of microbial control:

• Radiation damages DNA

• Ionizing radiation (x rays, gamma rays, electron beams)

• Nonionizing radiation (UV)

• Microvaes kill by heat; not especially antimicrobial)

Chemical methods of microbial control:

• Principles of effective disinfection

• Concentration of disinfectant 

• Organic matter

• pH

• Time 

Chemical methods of microbial control:

• Evaluating a disinfectant

  • Use-dilution test

1. Metal rings dipped in test bacteria are dried

2. Dried cultures placed in diluted disinfectant (according to manufacturers instructions) for min at 20 c

3. Rings transferred to culture media to determine whether bacteria survived treatment 

Chemical methods of microbial control:

• Evaluating a disinfectant

  • Disk-diffusion method

• Particular species are evaluated in each test

• Zone of inhibition must be at or beyond a certain diameter

Chemical methods of microbial control:

Phelolics:

disruption of the plasma membrane

• lysol , amphyl

  • o-phenylphenol

• Listerine

  • Thymol

• Pinesol

  • Turpineol

• dial soap

Chemical methods of microbial control:

Halogens

• Tincture of iodine (I₂)

  • Iodine denatures proteins by breaking disulfide bonds

• Betadine

  • Povidone iodines (linked to organic molecule) as in Betadine; denatures proteins by breaking disulfide bonds

• Sodium hypochlorite (NaOCl)

  • Is a strong oxidizing agent 

• Bromine tablets 

  • Used in hot tubs, pools kills by oxidation

• Chlorine gas

  • used in swim pools -oxidizing agent.

• Bromine and chlorine products are strong oxidizers 

Halogen:

What does iodine do?

•  denatures proteins by breaking disulfide bonds

Halogen:

What does betadine do?

• Povidone iodines (linked to organic molecule) as in Betadine; denatures proteins by breaking disulfide bonds

Halogen:

What does sodium  hypochlorite (NaOCl) do?

•  a strong oxidizing agent 

Halogen:

What do bromine tablets do?

• Used in hot tubs, pools kills by oxidation

Halogen:

What does chlorine gas do?

• used in swim pools -oxidizing agent.

Halogen:

Bromine and chlorine products are strong..

oxidizers

Types of disinfectants: alcohol

• Alcohols. Ethanol isopropanol

  • Denatures proteins, dissolves lipids 

What does alcohol do to proteins and lipids

Denatures proteins, dissolves lipids 

Heavy metals: denature proteuns by breaking disulfide bonds

• Mercurachrome antiseptic: for wounds

• Copper sulfate (CuSO4): algicide

• Zinc chloride (ZnCl2): mouthwashes

• Silver nitrate (AgNO3): antiseptic for eyes, wounds

Types of disinfectants: Surface active agents

• Surface-active agents or surfactants (soaps and detergents)

  • Soap: acid-anionic detergents

  • Degerming: sanitizing 

Quaternary ammonium compounds (quats):

• Disruption of plasma membrane, denaturation of proteins

• Benzalkonium chloride (aka Zephiran)

• Roccal: lab disinfectant

• cationic detergents

• Cetylpyridinium chloride (Cepacol)

Types of disinfectants: aldehydes

• Inactive proteins by cross-linkin with functional groups (–NH2, –OH, –COOH, —SH)
  – Glutaraldehyde, formaldehyde

• Disinfection of hospital equipment, especially in respiratory therapy, for kidney dialysis machines, endoscopes

Alkali and acids

• NaOH (sodium hydroxide) in some floor cleaners

• NH₄OH in ammonia, esp good at breaking down lipids

• Benzoic acids in mouthwashes; benzoic acid, sobic acid, citric acid, and ascorbic acid, in food products

Gaseous sterilants:

• Denature proteins

• Ethylene oxide to sterilize hospital equipments, disposable lab plasticware

Other oxidizing agents:

• O₃ (swim pools),

• H2O(skin),

• Cl₂ (swim pools)
  peracetic acid(dialysis equipment),

• bleach (sodium hypochlorite),

• bromine
  

• – Steals electrons from biomolecules, causing breakdown

Microbial characteristics and microbial control, image

Microbial characteristics and microbial control, image

Microbial Characteristics and Microbial Control, chart of chemical agents and their effectiveness

Chemical agent	Effective against	Effective against
	endospores	mycobacteria
phenolics	poor	good
quats	none	none
chlorines	fair	fair
Alcohols	Poor	good
glutaraldehyde	fair	good